rFLCorrCoeff <- function(lcdat1, lcdat2) {

A <- sum(cos(lcdat1)*cos(lcdat2)) ;  B <- sum(sin(lcdat1)*sin(lcdat2))

C <- sum(cos(lcdat1)*sin(lcdat2)) ;  D <- sum(sin(lcdat1)*cos(lcdat2))

E <- sum(cos(2*lcdat1)) ; F <- sum(sin(2*lcdat1))

G <- sum(cos(2*lcdat2)) ; H <- sum(sin(2*lcdat2))

n <- length(lcdat1) ; denom <- sqrt(((n*n)-(E*E)-(F*F))*((n*n)-(G*G)-(H*H)))

rFL <- 4*((A*B)-(C*D))/denom ; return(rFL)

}